Based upon our previous studies of the pathogenesis of periodontal disease in mono-infected rats and our current histometric and electron microscopic investigation of periodontal disease in conventional rats we propose to continue morphometric studies of the inflammatory infiltrate with special emphasis on fibroblastic changes which are thought to be of importance in connective tissue remodelling. Particular emphasis will be placed on intracellular collagen fibrils (ICC) and on the recently discovered cell polarity of fibroblasts and their movement within the periodontal ligament. The increase of fibroblast ICC and contact with lymphocytes and osteoclasts will be investigated since preliminary data indicate that such a relationship exists. EM autoradiography, cytochemistry freeze-fracture and in vitro techniques will be used to provide an integrated view of fibroblast function in the gingiva and PDL. A mouse model of periodontal disease will be studied in the "crinkled" strain placed on a high sucrose diet. Use of this system will permit EM autoradiographic studies of cell function in periodontal disease. We propose to continue immunocytochemical localization of Actinomyces surface antigen and corresponding antibody in the oral tissues of gnotobiotic rats monoinfected with Actinomyces naeslundii and A. viscosus. We hope to be able to relate the penetration of actinomyces surface antigens to cell and tissue changes within the periodontium. Part of this research plan will be concerned with elucidation of the role of fibroblasts in the maintenance of the principal fibers of the gingiva and the PDL. Based on our recent findings we suspect that active cell migration on existing principal fibers as a template is a necessary component needed to maintain the structural integrity of the PDL, while still permitting active turnover. This "template" is destroyed during periodontal disease--thus full regeneration is difficult and perhaps impossible.